1. Field of the Invention
The present invention relates to a device suitable for use in an acceleration sensor, for controlling the acceleration sensor mounted to an occupant seat movable in the longitudinal direction of a vehicle and provided to actuate a seat belt pretensioner and the like.
2. Description of the Related Art
As a seat belt system mounted to a vehicle, one is known which, for example, is provided with a pretensioner wherein a webbing securing an occupant is retracted a predetermined amount when the vehicle suddenly decelerates, thus removing the looseness of the webbing applied to the occupant by force.
With this type of pretensioner, there is one in which a take-up shaft of a webbing retractor is forcibly rotated so as to tighten a webbing. Another type is one in which a buckle is forcibly pulled so as to tighten a webbing. For example, the latter pretensioner is provided with a gas generator. A cylinder moved under gas pressure is attached to the gas generator and coupled to a buckle via a wire or the like.
A sensor detects a sudden deceleration of the vehicle and the gas generator is operated so as to instantaneously generate gas. The cylinder is moved by the gas. The resultant moving force is transmitted to the buckle via the wire so as to forcibly move the buckle, thereby tightening the webbing.
It is preferable that the seat belt pretensioner and the acceleration sensor be mounted to an occupant seat rather than a vehicle body such as the floor since their positions, relative to the seat, remain unchanged even when the occupant seat is positionally adjusted in the longitudinal direction of the vehicle. However, if the acceleration sensor is mounted to the seat, it is necessary to prevent the pretensioner from operating when a rapid acceleration in the moving end of the seat occurs.